The invention relates to a monolithic integrated semiconductor device.
Semiconductor devices are known that, in order to limit the breakdown voltage of transistors, especially Darlington transistors, have an oxide-separated metal cover electrode above the space charge region that is connected by means of a voltage divider to a certain potential between the base and the collector. The breakdown voltage is determined substantially by the voltage potential of the cover electrode and by the thickness of the oxide.
U.S. Pat. No. 4,618,875, FLOHRS, discloses this kind of Darlington transistor circuit, in which the cover electrode is formed on the surface of the substrate and extends across two spaced-apart zones of opposite doping. The maximum attainable breakdown voltage is equivalent to the voltage value resulting from the sum of the enhancement breakdown voltage and depletion breakdown voltage. However, it must be taken into account that the thermal oxides typically used in planar processes cannot be made arbitrarily thick, so that the maximum attainable voltage with such a device is limited.